The present invention generally relates to a pneumatically actuated device for driving fasteners fed from a magazine into a workpiece and more specifically to a pneumatic engine that employs a shifting cylinder sleeve to control the supply of air to and exhaust from the pneumatic engine.
A number of pneumatically operated devices have been developed for use in driving fasteners, such as staples and nails, into workpieces. These tools typically include an engine, a triggering system, and a head valve for controlling the flow of air to the engine. The engine generally includes a piston that is housed in a liner or sleeve, wherein the piston is coupled to a rod that extends through the liner and out of the nose of the tool. The triggering system controls the flow of compressed air to the main valve. The main valve is normally open to the atmosphere. When the triggering system is actuated, the main valve opens, simultaneously closing the path to the atmosphere and venting high pressure air that will act against the piston. The piston is pushed so that the rod that is attached thereto will apply a force to a fastener and thereby drive the fastener into a workpiece. When the triggering system is reset, or unactuated, the main valve closes, reopening the path to the atmosphere. The high pressure air that is over the piston is exhausted, allowing a charge of high pressure air that had been compressed by the movement of the piston to act against the opposite side of the piston to push it to its returned position.
Despite the wide spread use of such tools, several drawbacks have been noted. One such drawback concerns the main valve in that it adds a significant amount of weight and length to the tool. Another drawback concerns the mechanism by which the magazine assembly is mounted to the tool.
In one preferred form, the present invention provides a pneumatic fastening tool assembly that employs an engine having a sliding sleeve arrangement so as not to require a main valve for its operation, thereby reducing the overall weight and length of the tool.
In another preferred form, the present invention provides a pneumatic fastening tool having a housing assembly, a sleeve, a piston assembly, and a valve assembly. The housing assembly defines a housing cavity, an exhaust aperture and a rod aperture. The sleeve has a sleeve body and a flange formed about a perimeter of the sleeve body. The sleeve body defines a hollow cavity and includes a first end, a second end opposite the first end, and a supply port formed proximate the second end. The sleeve is movably disposed in the housing cavity such that the flange is adjacent a sleeve chamber. The piston assembly includes a piston, which is slidingly disposed in the hollow cavity of the sleeve body forwardly of the exhaust aperture and which segregates the hollow cavity into a first cavity portion and a second cavity portion, and a rod, which extends into the rod aperture and which is coupled to the piston such that translation of the piston within the hollow cavity causes likewise translation of the rod. The valve assembly is coupled to the housing assembly and operable in a first condition and a second condition. The first condition provides a first flow path that is adapted to supply in fluid connection a source of compressed air to the sleeve chamber to thereby bias the sleeve in a first direction along a longitudinal axis of the hollow cavity and into one of an extended position and a returned position. The second condition provides a second flow path that is adapted to vent the sleeve chamber to the atmosphere and bias the sleeve in a second direction opposite the first direction and into the other one of the extended position and the returned position. Positioning of the sleeve in the extended position provides a piston feed flow path, which is configured to route a supply of compressed air through the sleeve and into the second cavity portion to force the piston toward the rod aperture, and to block a flow of air to through the exhaust aperture. Positioning of the sleeve in the returned position blocks the piston feed flow path and permits air to flow from the second cavity portion through the exhaust aperture and to the atmosphere.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.